Plasma addressing structures may be employed in a variety of applications including data storage devices, video cameras, and flat panel liquid crystal displays. One such addressing structure is described in U.S. Pat. No. 4,896,149 of Buzak et al. for "Addressing Structure Using Ionizable Gaseous Medium." A preferred embodiment of this addressing structure includes an ionizable gas captured within each of multiple parallel channels extending across a display screen. The gas in each channel is selectively ionized to address a row of display elements aligned with the channel. The gas is ionized by a gas ionizing structure that includes an electrical reference electrode or anode and a data strobe electrode or cathode that extend along the length of each channel.
While the gas in a channel is ionized, data signals are delivered to the addressed display elements on multiple data lines extending perpendicular to the arrangement of channels. A liquid crystal material is responsive to the data signals to form a display image.
FIG. 1 is an elevated fragmentary view of a prior art glass substrate 10 within which multiple parallel channels 12 are inscribed for containing an ionizable gas. Each channel 12 has a generally semicircular cross section and a depth 14 measured from a top surface 16 of substrate 10. Adjacent channels 12 are separated by sidewalls 20 that define multiple support structures 22 with top surfaces 16 that support a liquid crystal material and other components (not shown).
A strobed row electrode or cathode 30 and a grounded reference electrode or anode 32 are positioned on a bottom surface 34 of each channel 12. Cathodes 30 and anodes 32 are relatively thin, narrow metal coatings covering less than about 35% of bottom surface 34, or about 25% of the interior surface of channels 12. Each of cathodes 30 receives a row strobe signal from a corresponding output amplifier 36 of a data strobe circuit 38 for selectively ionizing a gas contained within the channel 12.
Channels 12 have relatively large depths 14 of about 0.152 mm, which is about one-third the channel width 40. All surfaces abutting channels 12 other than cathodes 30 and anodes 32 are nonconductive and tend to quench the ionization of the gas. However, the relatively large depths 14 of channels 12 accommodate correspondingly large volumes of gas that overcome the quenching effects of the nonconductive surfaces. Specifically, the volume of gas increases as the third power of the channel dimensions, and the area of abutting surfaces increases as the second power of the channel dimensions. A larger volume of ionized gas is, therefore, capable of overcoming the quenching effects because the nonconductive surface is proportionally smaller.
A consequence of the large depths 14 of channels 12 is that substrate 10 is relatively difficult to manufacture with an acceptable yield. Moreover, the generally semi-circular cross section of deep channels 12 forms support structures 22 with relatively broad bases 42. In display systems, such support structures 22 form relatively wide black bands between the image lines formed on the display screen. Such support structures 22 also reduce the range of off-axis viewing angles from which the display screen may be viewed.